Question on aggregates and GIMPLE

[Richard Kenner]

    BTW, you can't call expr_size, since that generates rtl.  You have to
    re-implement what expr_size did on trees alone.

Sorry, I thought it generated trees, but you're of course right.  I thought
we had one that just did pure tree, but I guess it would be too trivial
since it's just a matter of passing the size and the expression to
SUBSTITUTE_PLACEHOLDER_IN_EXPR.